1. Field of the invention
The present invention relates to the automatic insertion of bundles of documents into envelopes, in particular in automatic mail processing machines.
2. Description of the prior art
Bundles to be inserted successively into envelopes may be formed of one or more sheets. In an automatic mail processing machine the insertion into envelopes is effected at the output from a folder or from a device for assembling or transporting bundles. The insertion devices may comprise pusher tabs or insert rollers which push the bundle into an envelope extracted from a pile of envelopes and offered up open on the trajectory of the bundle.
There is known, for example, from U.S. Pat. No. 3,412,995 a device of this kind with fingers which hold the bundle against the surface of a table to transfer them from a bundle entry station to an open envelope holding station. According to this document, the table is fixed to an upper frame on a carriage reciprocated in translation on guide rods. The clamping fingers are formed at the end of a pivoting arm inside the frame. By means of appropriate openings in the table, these fingers can be raised above the table or retracted. For the purpose of controlling the fingers, the arm is urged into a position such that its fingers are retracted but carries on its lower edge a peg which, in bearing on a guide surface provided in one of the rods, causes the raising of the fingers at the ends and beginnings of the forward and return strokes of the assembly. The guide surface defines a higher level on which the peg bears at the ends and beginnings of the forward and return strokes and a lower bearing level between these, transitional ramps linking the higher and lower levels.
During the forward stroke, the fingers are initially raised. The peg reaching the first transitional ramp corresponds to the raised fingers reaching the bundle. This transitional ramp then allows the fingers to drop so as to clamp against the surface of the table the bundle which is thus transported and inserted into the envelope. At the end of the same forward stroke the second transitional ramp causes the fingers to be raised again and release the bundle which is then pushed fully into the envelope.
During the return stroke, the clamping fingers are retracted during the travel of the peg over the lower level of its guide surface.
A device of this kind protects the bundle during its insertion into the envelope by virtue of the insertion of the table with the bundle into the envelope. On the other hand, the action of the clamping fingers urged into bearing engagement on the bundle and retained by the bundle during its transportation may damage it prior to its insertion and is therefore unsatisfactory.
One specific objective of the present invention is to eliminate this disadvantage. Another objective of the invention is to provide for the proper insertion of bundles of varying size into corresponding envelopes with the bundles protected throughout such insertion.